Melophorus cuneatus Heterick, Castalanelli & Shattuck

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 159-161

Melophorus cuneatus Heterick, Castalanelli & Shattuck sp. n.

Types.

Minor worker holotype (bottom ant) from Binningup 33°08'46"S, 143°43'15"E, Western Australia, 1 January 2007, Heterick, B.E., coastal scrubland, nest in small tussock [JDM32-001958] (WAM). Paratypes: 2 major workers on same pin and with same details as holotype (WAM); minor worker from Bold Park 31°56'S, 115°46'E, Western Australia, 19-22 March 2004, S. Callan [JDM32-001962] (ANIC); 2 major workers from Jandakot Regional Park 32°06'S, 115°53'E, Western Australia, 28 April 2002, N. Gunawardene, Pitfall trap T2, S7 [JDM32-001960] (BMNH).

Other material examined.

Western Australia: Jandakot Reg. Pk. (Gunawardene, N. [JDM32-001960]), Reabold Hill (Majer, J.D. [JDM32-001959]).

Diagnosis.

Melophorus cuneatus can be placed in the M. biroi species-group on the basis of characters of the clypeus, propodeum, mandible and palps. The species is placed in the M. biroi species-complex on the basis of a further suite of characters (viz, metatibia of major worker with only one preapical spur [except rarely in the mjobergi clade]; clypeal psammophore placed anteriorly at or just above anterior margin of clypeus in the minor worker and often in the major worker; head dorsoventrally compressed to varying degrees in the minor worker of most species with the eyes placed high on the sides; compact legs, and small body size [excluding mjobergi clade] HW of smallest minor 0.36 mm, average HW of smallest minors 0.46 mm; HW of largest known major 1.29 mm, average HW of largest majors [where known] 1.05 mm). Melophorus cuneatus cannot be confused with any other other Melophorus except, perhaps, for M. paramorphomenus , which, however, has the diagnostic characters of the M. fieldi complex. In profile, the propodeal dorsum of minor and media workers of M. cuneatus is extremely narrow and almost acuminate, the metanotal groove in all workers is narrowly and deeply impressed, the mesonotum of the minor worker is hypertrophied so that the metathoracic spiracle is situated on its underside in a distinctly lateral position and all workers possess weak pubescence and a moderate number of erect setae on the mesosoma.

Minor worker description.

Head. Head square; posterior margin of head planar or weakly convex, or planar or weakly concave; frons matt or with weak sheen, microreticulate or microreticulate-shagreenate; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye moderate (eye length 0.20-0.49 length of side of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae concave; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin straight, or broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron matt or with weak sheen and microreticulate throughout; anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; appearance of erect pronotal setae short, (i.e., longest erect setae shorter than length of eye) and unmodified; in profile, metanotal groove a narrow but deep slit; propodeum matt or with a weak sheen and microreticulate-striolate; propodeum wedge-shaped, tapering dorsad; length ratio of propodeal dorsum to its declivity not applicable, propodeal dorsum reduced to a narrow sliver; erect propodeal setae variable in number, may be absent; appressed propodeal setulae long and closely aligned, creating pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and longer (length ≥ 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth with vestigial sculpture. Gaster. Gaster weakly shining with indistinct shagreenation; pilosity of first gastral tergite consisting of thick, appressed setae that form pubescence, interspersed with numerous short, bristly, erect setae. General characters. Colour of foreparts chocolate to black, gaster dark brown to black.

Major worker description.

Head. Head square; posterior margin of head weakly concave; cuticle of frons shining with superficial shagreenation or microreticulation only; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye moderate (eye length 0.20-0.49 length of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae straight, divergent posteriad; frontal lobes straight in front of antennal insertion. Anterior clypeal margin broadly emarginate; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth num bers two and four; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and uniformly microreticulate, with shallow dimpling evident on the dorsum of the mesonotum; anterior mesosoma in profile steeply rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on a higher plane than propodeum; erect pronotal setae short, (i.e., shorter than length of eye) and unmodified; in profile, metanotal groove a narrow but deep slit; propodeum shining and microreticulate; propodeum always smoothly rounded; propodeal dorsum and declivity confluent; erect propodeal setae present and sparse to moderate (1-12); appressed propodeal setae long, each reaching setae behind and in front, but not forming pubescence; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded, or generally rounded with median indentation; node shining and smooth with vestigial microreticulation anteriad. Gaster. Gaster shining, shagreenate ('LP record’ appearance); pilosity of first gastral tergite consisting of longish, closely aligned, appressed setae interspersed with short, bristly, erect setae (some distally flattened). General characters. Colour of foreparts russet to dark reddish-brown, gaster dark brown to brownish-black.

Measurements.

Worker (n = 4): CI 98-115; EI 19-27; EL 0.14-0.23; HL 0.52-1.06; HW 0.52-1.23; ML 0.77-1.35; MTL 0.45-0.73; PpH 0.05-0.12; PpL 0.30-0.59; SI 73-129; SL 0.67-0.89.

Comments.

Melophorus cuneatus is confined to the southwest of Western Australia. All known records have been from the Swan Coastal Plain. This ant is nowhere common, but appears occasionally in collections from relictual bushland in the Perth metropolitan area as well as localities to the south as far as Binningup. The appearance of the mesosoma, in particular the wedge-shaped propodeum, distinguishes minor workers of this ant from all others. The major worker is less spectacular but has weak pubescence on the gaster and a deeply impressed metanotal groove, both of which serve to differentiate it from other members of the complex that occur in the same area. No material has been available for sequencing, but the morphology suggests a close relationship to M. propebiroi . There are no ecological notes on labels for this species, but the localities where it has been found support dry sclerophyll woodland.

Etymology.

Latin cuneatus ( ‘wedge-shaped’); adjective in the nominative singular.